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In this article, an improved short-term speed prediction method is proposed to predict short-term future speed and analyze future energy consumption of intelligent fuel cell vehicles. The short-term future speed is predicted by the proposed Inflated 3-D Inception long short-term memory (LSTM) network, which takes the spatiotemporal-vision information and vehicle motion states. Specifically, the spatiotemporal-vision-based deep neural network utilizes image sequences captured by a front-facing camera as environmental information and historical speed series as motion information to improve the prediction accuracy. Then, a case study of the proposed speed prediction method, with rule-based energy management strategy to calculate future energy consumption, is presented. The simulation results show that short-term speed prediction based on the Inflated 3-D Inception LSTM network can achieve high accuracy of speed prediction in various traffic densities, as well as low prediction errors of future energy consumption including the hydrogen consumption and state-of-charge attenuation. This work was supported in part by the National Key Research and Development Program under Grant 2018YFB0105402 and Grant 2018YFB0105703, in part by the Fundamental Research Funds for the Central Universities under Grant 2019CDXYQC0003, Grant 244005202014, 2019, and Grant 2018CDXYTW0031, in part by the National Natural Science Foundation of China under Grant 51806024, in part by the Chongqing Research Program of Foundation and Advanced Technology under Grant cstc2017jcyjAX0276, and in part by the Venture and Innovation Support Program for Chongqing Overseas Returnees under Grant cx2018051.

Hydrogels and organogels, as two crucial representatives of soft materials, have attracted immense interest. However, they develop independently along two parallel lines, and these gels with single networks have their inherent drawbacks. For example, hydrogels tend to freeze, and organogels are usually brittle. Herein, organogels were incorporated into a hydrogel matrix for the synthesis of organohydrogels GOHs through polymerization in Pickering emulsion. The rigid organogel domains contribute to enhancing the strength of organohydrogels. Besides this, the organogels derived from 12-HAS self-assembly behavior exhibit a gel-sol transition when the temperature reaches 70 °C, thus leading to a thermo-softening behavior in the GOHs. Due to the phase transition of organogel domains and the elastic hydrogel network, the resultant organohydrogels demonstrate high-strain shape-memory performance (over 1000%) which could help achieve full recovery in seconds. Consequently, GOHs are endowed with the potential of practical application in soft robots, wearable devices, and biological materials.

An ultraviolet (UV)-protective cotton fabric has been developed by combining tannic acid and copper ions (TA-Cu) on cotton fabrics. The structure and properties of TA-Cu and cotton fabrics finished...

Milling stability is a function of the tool point frequency response functions (FRFs), which vary with the movements of the moving parts within the whole machine tool work volume. The position-dependent tool point FRFs result in uncertain prediction of the stability lobe diagram (SLD) for chatter-free machining parameter selection. Taking the variations of modal parameters to represent the variations of tool point FRFs, this paper introduces the edge theorem to predict the robust milling chatter stability. The application of the edge theorem requires the minimum and maximum modal parameters within the machining space defined by the machining position and machining allowance information. Then, radial basis function artificial neural networks (RBFANNs) are used to predict the position-dependent modal parameters in X and Y directions based on the sample information of machining positions and related modal parameters at the tool point. Moreover, sample machining spaces are determined based on the aforementioned sample positions, and the trained RBFANNs are used to obtain corresponding sample extreme modal parameters. On this basis, RBFANNs for predicting the position and machining allowance-dependent extreme modal parameters can also be trained, and they are combined with the edge theorem and zero exclusion condition to calculate robust pairs of the spindle speed (n) and limiting axial cutting depth (aplim) and then plot the robust SLD (RSLD). A case study was performed on a real three-axial vertical machining center, and the plotted RSLD considering position variations was compared with the traditional SLD. Results of the chatter tests show that the RSLD can provide more reliable (ap, n) pairs to guarantee the milling stability, validating the feasibility of the proposed robust milling chatter stability prediction method.

The derivatives of ferrocene with redox properties are widely used. Some studies have used complex synthesis processes to obtain surfactants with redox properties. In order to simplify the synthesis process, FA-DMDA-Ox, a surfactant with redox and pH dual responses, was prepared by simple electrostatic interaction between ferrocenecarboxylic acid (FA) and N,N-dimethyldodecylamine (DMDA). A stable oil-in-water emulsion was prepared by using FA-DMDA-Ox at 25 °C. When sodium sulfite was added to the emulsion, the emulsion was demulsified. This was due to the oxidized ferrocene group that was reduced from the charged hydrophilic state to the uncharged hydrophobic state, which destroyed the original surface activity. In addition, when added HCl or NaOH to the emulsion changed pH, demulsification was caused by the dissociation of FA-DMDA-Ox.

CO2-responsive microemulsions based on ionic liquid 1,1,3,3-tetramethylguanidine-oleic acid (TMG-OA) have been designed to provide an approach for reducing the volatilization of amine in amine-containing microemulsions effectively and exhibit reversible transitions of microstructures. The ionic liquid TMG-OA was prepared by the direct neutralization of oleic acid (HOA) and 1,1,3,3-tetramethylguanidine (TMG, one of volatile and toxic amines). From the investigations of nuclear magnetic resonance hydrogen spectrum, pH, thermogravimetry, and automatic interface tension meter, the excellent properties of switchability, stability, and surface activity of TMG-OA were demonstrated, and then the ionic liquid-based microemulsions with CO2 response were prepared with TMG-OA (surfactant), HOA (oil phase), isopropyl alcohol (IPA, cosurfactant), and water. Interestingly, for microemulsions with a higher IPA content (47.42, 44.48 wt %), sizes of microemulsions are increased upon introducing CO2 and decreased upon addition of N2/65 °C. In addition, for microemulsions with a lower IPA content (26.22 wt %), the new microemulsions with different sizes are regenerated after the phase separation of emulsions generated by introducing CO2, and incomplete recovery of microemulsions can be observed upon addition of N2/65 °C. The reversible microstructures are induced by the swelling behavior and the reduced single phase area, which are caused by the reversible conversion between TMG-OA and HOA components.

Poly(ionic liquid)s brush-grafted carbon dots (CDs-PILs-X) were synthesized for the first time by surface-initiated atom transfer radical polymerization, where X representing polymerization time was 1, 3, 6, 12, and 18 h. Their tribological properties as lubricant additives of polyethylene glycol (PEG200) were evaluated under the steel/steel contact and linear reciprocating mode. The CDs-PILs-1 exhibited the best friction-reducing and antiwear performance at a concentration (c) of 1.5 wt%. Specifically, the friction coefficient and wear volume of PEG200 were reduced by 61.9% and 82.5%, respectively. At a concentration (c) of 1.5 wt%, the performance of CDs-PILs-1 apparently outperformed that of PILs-1, reflecting the particularly important role of carbon cores in boundary lubrication. In addition, the CDs-PILs-1 was comparable to CDs-PILs-3 and much superior to CDs-PILs-6-18, suggesting that the carbon cores and PILs shells of CDs-PILs played a synergistic lubrication effect and an optimal degree of polymerization of 3.0 (close to that of CDs-PILs-1) should exist. Wear scar surface analyses revealed that robust boundary tribofilms with a thickness of approximately 190 nm, that is, the tribochemical film embedded with carbon cores, were formed on the sliding surfaces lubricated by CDs-PILs-1 dispersion, directly accounting for the excellent tribological properties of CDs-PILs-1.

Energy management strategy (EMS) is very crucial for the hybrid power system of fuel cell range extender vehicles (FCREV) with respect to improving vehicle energy consumption economy. The objective of this article is to formulate a real-time EMS to efficiently regulate the energy flow of the hybrid power system under complex driving conditions. First, a nonlinear control system is developed to calculate the reference output current of the proton exchange membrane FC for energy management, and the theoretical stability of the nonlinear control system is proven by using the Lyapunov function. Then, a physics-based model of FCREVs is established in the Simulink environment, which considers the energy losses from the braking and the mechanical transmission system. Finally, fuzzy logic control is proposed as a benchmark to compare the performance of the proposed EMS in a combined driving cycle testing condition. The simulation results show that the proposed EMS has the potential for prolonging the lifespan of FC and achieves optimal energy consumption efficiency of FC, as well as improving the energy consumption economy of FCREVs.

This study aims to reveal the mechanism of variable fan speed control in Open cathode PEM fuel cell (OC-PEMFC) by the experiments, which analyze the effects of variable fan speed on the operating parameters under different fuel cell loads. The operating parameters are cell temperature, stack voltage, voltage uniformity, and parasitic power. The results reveal that the fan speed has strong effects on the operating parameters: (1) it affects the temperature distribution and overheats the middle cells of fuel cell stack, especially, when it operates at high power; (2) it affects the variation trend of the voltage under different loads; (3) it affects the voltage uniformity, which can be improved via forced convection; (4) it affects the system efficiency due to the parasitic load consumed by the fan. Considering the varying effects of these operating parameters on performance, durability and system efficiency under different fuel cell loads, the variable fan speed control should adapt the variation of fuel cell loads and weigh multiple operating parameters.

The efficiency, reliability and lifespan of the fuel cell are strongly affected by the dynamic load variation of its output, which renders it desperate to investigate the influence of the power change rate on the fuel cell. In this study, three data dimensionality reduction algorithms are applied to identify the power change rate of the fuel cell in a less time-consuming way. To achieve that, the cell voltages of the stack as high-dimensional dataset is instantly projected onto the one-dimensional eigenvector space by principal component analysis (PCA), Fisher discriminant analysis (FDA) and locally linear embedding (LLE), respectively. The eigenvalue of one-dimensional eigenvector has the potential for instantly identifying the power change rate of the fuel cell and can be used as a feedback parameter in the control, which can improve the dynamic response, reliability, and lifespan of the fuel cell stack. According to the performance indicators of the algorithms including monotonicity, linearity and program execution time, the result shows that the PCA algorithm is the best-matched method for the real-time control of the fuel cell system. In the end, this study discussed some potential applications of this method in the fuel cell system, be it to be used alone or in a vehicular fuel cell hybrid system.

Branched polyethyleneimine (PEI) grafted carbon dots (CDs-PEI0.6-10k) were facile synthesized by hydrothermal treatments of citric acid and PEI with various molecular weights of 0.6, 1.8 and 10 k. With the aid of protonation and anion exchange (between Cl− and bistrifluoromethanesulfonimide abbreviated as NTf2-) processes in aqueous phase, the branched polyelectrolyte grafted CDs (CDs-PEI0.6-10k-NTf2) derived from CDs-PEI0.6-10k were gained as the precipitates. The tribological properties of CDs-PEI0.6-10k-NTf2 as the lubricant additives of polyethylene glycol (PEG200) were evaluated. The CDs-PEI0.6-10k-NTf2 exhibited superb friction-reducing and antiwear performances followed the sequence: CDs-PEI10k-NTf2 > CDs-PEI1.8k-NTf2 > CDs-PEI0.6k-NTf2. Typically, the friction coefficient and wear volume of PEG200 reduced by 53.8% and 79.9%, respectively, when only 0.07 wt% of CDs-PEI10k-NTf2 was introduced. The surface analysis results revealed that a tribochemical reaction film composed of iron compounds (including iron fluorides, sulfates, nitrides, oxides and carbides) and organic compounds containing various elements (such as C, O, N, S and F) should form on the rubbing surfaces lubricated by CDs-PEI10k-NTf2 (0.07 wt%)/PEG200 dispersion. The distinguished friction-reducing and antiwear properties of CDs-PEI10k-NTf2 could be attributed to their nanolubrication effects and the above tribochemical film, i.e. the synergistic lubrication effect of their carbon cores and surface groups.

Similar to the responsive behaviors of emulsions under salt-free conditions, precise control of emulsification and demulsification is also required in some applications under saline conditions, especially in crude oil production and transport. So far, few studies have focused on the preparation of the responsive emulsions under saline conditions. In this study, CO2 responsive emulsions were prepared in the presence of NaCl using a fatty acid soap M-DA as stabilizer. M-DA complex was synthesized through electrostatic interactions between dimeric acid (DA) and Jeffamine (M1000). The droplet size and morphology of the oil–brine emulsions were characterized by dynamic light scattering and transmission electron microscopy, respectively. The oil–brine emulsion maintains high stability under air but completely separates into two phases upon exposure to CO2. NaCl plays a significant role in the CO2-induced demulsification, including salting-out effect and screening of electrostatic repulsion. It is worth noting that in the absence of NaCl, the emulsion remained stable after CO2 bubbling. CO2 responsive emulsions can also be prepared in the presence of other salts, or with other fatty acid soaps, which presents more interesting possibilities for preparation of CO2 responsive emulsions under saline conditions.

Hydrophobic long carbon chains (C16) were grafted onto the main chains of Xanthan Gum by etherification under the ordered conformation of Xanthan. Rheology and pyrene fluorescence spectroscopy expe...

Hydrophobic associating polyacrylamide (PDH) was prepared via aqueous dispersion polymerization in the presence of ammonium sulfate. In order to dissolve the polymer at high salt solution c...

Reform of the Chinese petroleum industry has entered its second phase since early 1999. The productivity of the petroleum industry has been greatly improved, while the safety performance and records are not satisfactory. This paper investigates the critical factors for improving safety performance in the Chinese petroleum industry. The data used for the analysis are from a questionnaire survey administered to 480 professionals in the petroleum industry in which 143 valid responses were received. Statistical analysis techniques are used to analyze the data collected. The findings revealed that the most significant source of the safety problem is due to the combination of several reasons, including (a) violation on operating procedures, (b) obsolete facilities and equipment failures, (c) insufficient safety management system, (d) improper commands, number of casualties, and (e) production performances and operating skills. The three most essential protective methods include safety training and increasing staff’s safety consciousness, cultivating safety culture, and enhancing equipment management and detecting hazards in time.

The ozone mass transfer efficiency based on deionized water of both the PTFE hollow fiber membrane aeration and ultrasonic-assisted PTFE hollow fiber membrane aeration processes have been studied and described by mass transfer coefficient (KLa). Bubble size distributions were also investigated via an image-technology to analyze mass transfer processes. All the PTFE hollow fiber membranes were hydrophobic and had an asymmetrical structure. Results showed that the maximum value of KLa (0.438 min−1) was obtained at an intake flow rate of 300 L/h with 1# membrane (0.22 µm) in single membrane aeration system. This gas-liquid mass transfer was strongly dependent on pressure. After the introduction of ultrasonic power, the KLa value reached 0.632 min−1 with an ultrasonic power of 1000 W. This enhancement was related to the periodical replacement of local liquid at the interface between the bulk solution and the liquid with high concentration of ozone. The degradation of sulfonated phenolic resin (SMP) confirms that its mineralization was promoted by the enhanced gas-liquid mass transfer of ozone and the generation of OH in the bulk solution.

Reusing retired electric vehicle batteries (REVBs) in renewable energy systems is a relatively new concept, and the presented PV-hydrogen-REVB hybrid energy system is a promising way to exploit REVBs’ residual capacities. This paper focuses on the design and sizing optimization of the entire system and delivers three main contributions. First, this paper proposes a REVB model based on the model of capacity fading of lithium battery cells, which could allow a more realistic result for the design. Second, a power management strategy is presented to regulate the energy flow, for protecting the REVB and other system components. Third, multiple objectives are considered in the optimization model, including minimizing loss of power supply, system cost, and a new indicator, namely, potential energy waste. Then, using the simulation results of a five-year working period to calculate the objective functions, a multi-objective evolutionary algorithm NSGA-II is applied to generate the Pareto set of a case for residential usage. In further discussions, the influences of ignoring REVB’s capacity fading and removing the objective of potential energy waste possibility are presented, as well as the comparison of performances between NSGA-II and MOEA/D. The results reveal that the reliability of the system is impaired if ignoring the REVB’s capacity loss, and the proposed indicator is crucial for the design. NSGA-II has a better performance regarding the distribution of solutions and gives better results in this study.

Ionic liquid modified CDs and novel thin nanosheets constructed graphitic carbon nitride (g-C3N4) microspheres were synthesized by the template method and by calcination of a supramolecular precursor, respectively. The CDs were decorated onto the surface of g-C3N4 by solvothermal treatment to tune the visible-light photocatalytic degradation performance of g-C3N4. The CDs could not only form heterojunctions with g-C3N4 by chemical bonding, π–π stacking and electronic attraction interactions, but also change the surface charges of g-C3N4 from negative to positive. The roles played by heterojunctions and surface charges in the photocatalytic performance of CDs (1.6 wt%)/g-C3N4 composites were explored by photocatalytic degradation of anionic (methyl orange, MO), nonionic (p-nitrophenol, p-NP) and cationic (methylene blue/rhodamine B, MB/RhB) pollutants. Compared with g-C3N4, the composite showed obviously higher and lower photocatalytic activity for MO/p-NP and MB/RhB degradation, respectively. These results demonstrated that the surface charges might play a positive or negative but dominant role by enhancing or inhibiting the absorption of pollutant molecules despite the fact that heterojunctions always played a positive role by promoting the light-harvesting ability and separation efficiency of photo-generated electron–hole pairs of g-C3N4.

The mutual understanding between driver and vehicle is critically important to the design of intelligent vehicles and customized interaction interface. In this study, a deep learning-based joint driver behavior reasoning system toward multi-scale and multi-tasks behavior recognition is proposed. Specifically, a multi-scale driver behavior recognition system is designed to recognize both the driver's physical and mental states based on a deep encoder-decoder framework. The system jointly recognizes three driver behaviors, namely, mirror-checking, lane change intention, and emotions based on the shared encoder network. The encoder network is designed based on a deep convolutional neural network (CNN), and several decoders for different driver states estimation are proposed with fully connected (FC), and long short-term memory (LSTM) based recurrent neural networks (RNN), respectively. The proposed framework can be used as a solution to exploit the relationship between different driver states for intelligent vehicles towards an efficient driver-side understanding. The testing results on the Brain4Car dataset show accurate performance and outperform existing methods on driver postures, intention, and emotion recognition.

Capillary flow of water in an array of open nanotextured microgrooves fabricated by femtosecond laser processing of silicon is studied as a function of temperature using high-speed video recording. In a temperature range of 23&ndash, 80 &deg, C, the produced wicking material provides extremely fast liquid flow with a maximum velocity of 37 cm/s in the initial spreading stage prior to visco-inertial regime. The capillary performance of the material enhances with increasing temperature in the inertial, visco-inertial, and partially in Washburn flow regimes. The classic universal Washburn&rsquo, s regime is observed at all studied temperatures, giving the evidence of its universality at high temperatures as well. The obtained results are of great significance for creating capillary materials for applications in cooling of electronics, energy harvesting, enhancing the critical heat flux of industrial boilers, and Maisotsenko cycle technologies.

Surveys were delivered to the occupants of two university buildings in Sydney Australia to collect occupant perceptions related with energy use and the impact of the ���green��� rating in occupant behaviour. Overall, 100 surveys were delivered in a 6-star building, rated according to the certification system Green Star, and in a non-rated building, from Western Sydney University. Occupants were inquired about their perception and interactions with heating, cooling, lighting, windows/doors opening, windows blinds and plug loads. This made possible to understand if there is a significant difference in energy-related occupant behaviour when comparing a green-rated to a non-green-rated building. Additionally, this study analysed if occupant���s gender, age and work role, as well as the characteristics of the built environment have impact on occupant behaviours and actions. It was possible to conclude that the ���green��� rating has no impact in the way occupants interact with the buildings��� systems, and variables such as gender, age and the characteristics of the built environment have impact in the way occupants interact with the building features and systems. The results were obtained according to statistical analysis and intend to be a guideline for future research in the field of energy-related occupant behaviour.

With the booming microwave and terahertz technology for communication, detection, and healthcare, the consequently increasingly complicated electromagnetic environment is in urgent need of high-performance microwave and terahertz absorption materials. However, it is still a huge challenge to achieve consecutively strong absorption in both microwave and terahertz regimes. Herein, an ultra-broadband and highly efficient absorber for both microwave and terahertz bands based on the monolithic three-dimensional cross-linked Fe3O4/graphene material (3DFG) is first reported. The 3DFG shows an incredible wide qualified absorption bandwidth (with reflection loss less than −10 dB) from 3.4 GHz to 2.5 THz, which is the best result in this area by far. Furthermore, the remarkable absorption performance can be maintained under oblique incidence, different compressive strains, and even after 200 compression/release cycles. The designed highly porous structure for minimizing surface reflection combined with the micro–ma...

Using CO2 as gasification agent instead of steam in in-situ coal gasification chemical looping combustion (iG-CLC) power plant can eliminate energy consumption for steam generation, thus obtaining higher system efficiency. In this work, a comparative study of iG-CLC power plant using steam and CO2 as gasification agent is concentrated on. The effects of steam to carbon ratio (S/C) and CO2 to carbon ratio (CO2/C) on the fuel reactor temperature, char conversion, syngas composition and CO2 capture efficiency are separately investigated. An equilibrium carbon conversion of 88.9% is achieved in steam-based case as S/C ratio increases from 0.7 to 1.1, whereas a maximum conversion of 84.2% is obtained in CO2-based case with CO2/C ranging from 0.7 to 1.1. Furthermore the effects of oxygen carrier to fuel ratio (φ) on system performances are investigated. Increasing φ from 1.0 to 1.4 helps to achieve char conversion from 75.9% to 88.9% in steam-based case, by contrast the char conversion can achieve 66.3%–84.2% in CO2-based case within the same φ range. In terms of iG-CLC power plant, recycling partial CO2 to the fuel reactor improves the overall performance. Approximately 3.9% of net power efficiency are increased in CO2-based plant, from steam-based plant. Higher CO2 capture efficiency and lower CO2 emission rate are observed in CO2-gasified iG-CLC power plant, expecting to be 90.63% and 85.18 kg·MW− 1·h− 1, respectively.

The application of hydrophobic associating polyacrylamide (HAPAM) was restricted due to the poor solubility. In order to enhance the solubility of HAPAM and avoid environmental pollution, aqueous two-phase polymerization was used to prepare HAPAM in ammonium sulfate aqueous solution and a milky dispersion was obtained. The HAPAM particles dispersed in the solution spherically and the average particle size was about 7.4 μm. The hydrophobic associating polyacrylamide prepared with aqueous two-phase polymerization exhibited superior solubility and it could dissolve completely in twenty seconds. HAPAM solution could aggregate to network through inter-molecular association, leading significant increase of viscosity. Moreover, the viscosity of HAPAM solution increased with addition of inorganic salt even in nearly-saturated solution, and the viscoelasticity of HAPAM solution also enhanced obviously in the presence of salt, exhibiting excellent salt resistance. Furthermore, anionic surfactant of sodium dodecyl sulfate (SDS) could aggregate with the cationic hydrophobic monomers on the polymer chains via electrostatic attraction to form mixed micelles, which could prompt the polymer from intra-molecular association to inter-molecular association, leading remarkable increase of viscosity and viscoelasticity of the solution. In addition, The HAPAM dispersion doesn’t contain any organic solvent and could become solution instantaneously once dilution into water, which provides a green and environmentally friendly strategy for preparation of hydrophobic associating polymers. The HAPAM dispersion was well fit for the hydraulic fracturing in shell gas due to the excellent solubility and environmentally friendly property. These features indicated that HAPAM dispersion would have a great potential application in hydraulic fracturing in shell gas.

Utilizing CO2 switchable surfactant and formation of wormlike micelle, a potential CO2-in-water (C/W) foam fluid concept is proposed, which might give us a fantastic approach to recovering the surfactant composition. For this objective, CO2 responsiveness of N,N-dimethyl oleoaminde-propylamine (DOAPA) and surface activity of DOAPA in the presence of CO2 were verified. After bubbling CO2, aqueous solutions of DOAPA with sodium salicylate (NaSal) at molar ratio 1:1 were created of high apparent viscosity because of the formation of wormlike micelle. The results from 1H NMR, dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM) studies indicated that CO2 responsiveness of DOAPA@NaSal was related to DOAPA and a network wormlike structure formed in the solution. DOAPA@NaSal C/W foam stabilized with wormlike micelle displayed good thermal adaptability and thermal stability, and might be expected to be a practical fracturing fluid for coalbed methane extraction. Moreover, DOAPA...

Carbon dots (CDs) were facilely synthesized by one-pot pyrolyzing a lactic acid-ionic liquid (IL) gel with a relatively high yield of 34.9 wt%. The CDs, with a mean particle size of 4.4 nm and high thermal stability, were almost amorphous and capped by IL groups. The CDs-IL in water exhibited an obvious excitation-, concentration-, pH-dependent and high salt-tolerant photoluminescence property. Specifically, the CDs-IL emitted the strongest blue fluorescence at 454 nm under 365 nm excitation with a quantum yield of 16%. In addition, the CDs-IL, as a kind of water-based lubricant additives, greatly improved the tribological properties of base liquid. The loading capability of base liquid for steel–steel pair increased from 50 N to at least 80 N when only 0.015 wt% of CDs-IL was added. Meanwhile, the mean friction coefficient and wear volume of base liquid reduced by 57.5% and 64% at the load of 40 N, respectively. In addition, the friction-reducing and antiwear performance of CDs-IL was far superior to the CDs and IL, reflecting a synergetic lubrication effect between the IL groups and carbon cores. Based on the worn surface analyses, the CDs were prone to be squeezed out of the rubbing surfaces during the boundary shear friction process, while the CDs-IL were prone to quickly form ordered absorption layers on rubbing surfaces by electrostatic interaction between the IL groups and steel surface, which is of key importance for the formation of effective lubrication film to largely reduce friction and wear.

The non-hydrophobically associating water-soluble polymer (DPAM) of acrylamide (AM) and dimethylamino propyl methacrylamide (DMAPMA) was synthesized. Then pH-switchable and CO2‑switchable viscoelastic liquids based on DPAM and anionic surfactant sodium dodecyl sulfate (SDS)(referred to as DPAM-SDS) were developed. When minor HCl aqueous solution was added into the DPAM and SDS aqueous mixture or CO2 was bubbled into it, the tertiary amine groups of DPAM were protonated to form quaternary ammonium groups, some of which in the same quaternary ammonium groups of DPAM “bridged” some SDS through noncovalent electrostatic attraction, behaving like a pseudo-hydrophobically associating water-soluble polymer and forming viscoelastic fluids as checked through environmental scanning electron microscope(ESEM) and rheology. Upon removing of CO2 or back of pH by minor NaOH aqueous solution, the quaternary ammonium species of DPAM were deprotonated back to tertiary amine groups, separating the pseudo-hydrophobically associating water-soluble polymer back to DPAM and SDS molecules, which resulted in forming low-viscosity water solution. The switchable viscoelastic conversion can be repeated.

A surfactant-free microemulsion (SFME) with CO2 stimuli responsive properties was prepared. The oil and the water phases were N, N-dimethylcyclohexylamine (DMCHA) and deionized water, respectively, and N, N-dimethylethanolamine was used as an amphisolvent. The single-phase and multiphase zones were measured by the ternary-phase diagram, and the microstructure of the SFME was determined by measuring the change trend of the electrical conductivity of the system with increasing DMCHA content. While using methyl orange as a probe, the microstructure of the SFME was further confirmed by an UV-visible spectrometer. The microstructures of water-in-oil (SFME-I) and oil-in-water (SFME-II) microemulsions were obtained by changing the DMCHA content in the system. The SFME-I system has a significant phase separation after the action of CO2. However, with the continuous introduction of CO2, the upper phase of DMCHA is gradually protonated and dissolves in the aqueous phase, resulting in a gradual decrease in the volume of the upper phase, and eventually in an aqueous solution of ammonium bicarbonate. For SFME-II, CO2 does not directly cause phase separation, but eventually it becomes an aqueous solution of ammonium bicarbonate with the addition of CO2. Both the water-in-oil structure SFME-I and the oil-in-water structure SFME-II have excellent CO2 stimuli responsive performance.

The anionic surfactant sodium oleate (NaOA) can self-assemble in aqueous solution in the presence of counter-ion inorganic salts to form wormlike micelles (WLMs), which exhibited viscoelast...

Ionic liquid functionalized graphene oxides (GOs-IL) were synthesized by the amidation and cation-π stacking, and their tribological property as the water-based lubricant additives was investigated...

In this work, using the pentaerythritol with phthalic anhydride and different long-carbon chain alcohols to synthesize a kind of hyperbranched polyester (FI) as flow improver for crude oil. The evaluation test shows FI could decline the viscosity by 65% at most on 50 °C, from 33430 mPa·s to 11670 mPa·s. Through further analyzed, TGA results confirm the designed compounds was successfully synthesized. XRD demonstrates the mixed carbon chain matched with the carbon chain distribution of saturated hydrocarbon have better ability than the single on inserting into the wax crystal. IR results indicate the reaction between the carboxyl of FI and the amino hydroxyl and hydroxyl of asphaltene and resin respectively. SEM photographs show FI react to the asphaltene and resin on the macro. In the further, the assembly model presents the FI with hyperbranched structure could increase the separation effect to improve the flowability of the crude oil.

N-Doped carbon dots (CDs) were directly synthesized with a high yield of 21.85% by one-pot pyrolysis of a gel composed of ethanolamine and 1-carboxyethyl-3-methylimidazolium chloride at 220 °C for 2 h. The as-synthesized CDs with a mean particle size of 7.8 nm were uniform, amorphous, and abundant in nitrogen content (23.15 wt%) and surface groups such as amide and hydroxyl. Thus, the CDs exhibited good water-solubility, bright blue excitation- and pH-dependent fluorescence with a quantum yield of 17.93%, and high ionic strength tolerance. In addition, a CD-based fluorescent sensor towards Cr(vi) ions with favorable sensitivity and selectivity was constructed based on the inner filter effect. Two good linear relationships between the concentration of Cr(vi) ions and the PL quenching efficiency were obtained in the ranges from 0.2 to 2 (R2 = 0.9965) and 2-40 μM (R2 = 0.9918), and the limits of detection (LOD = 3σ/S) were calculated as 0.018 and 0.25 μM, respectively. Importantly, this sensor was solid and capable of rapidly detecting Cr(vi) ions in tap water with detection ranges of 0.2-2 (R2 = 0.9817) and 2-60 μM (R2 = 0.9902), LODs of 0.048 and 0.40 μM, and recoveries of 102.1-106%.

A viscoelastic fluid, composing of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) at a mole ratio of 0.75 has been synthesized in the present investigation along with the incorporation of N, N-dimethylcyclohexylamine (DMCA) to endow CO2 responsive property into it. In present of CO2, DMCA was found to be protonated into quaternary ammonium salt, and thus converted to water soluble species. With addition of DMCA, the system transforms from gel-like fluid to water-like system, and subsequently self-assemble to form viscoelastic fluid after spraying of CO2. The rheological measurements and cryo-transmission electron microscopic (Cryo-TEM) characterization revealed that, the sol–gel transition was associated with the spherical-wormlike miceller transformation. This transformation was found to be reversible in nature. The micelle structures, molecular states and intermolecular interactions were exploited to achieve at the most plausible mechanism associated to the transformation.

It is a great challenge to fabricate lightweight microwave absorption materials (MAMs) with strong electromagnetic wave attenuation over wide frequency range. In this work, ultralight multiwalled carbon nanotube (MWCNT)/graphene foams (CGFs) are prepared through a facile solvothermal method and their microwave absorption (MA) properties are fully investigated. The CGFs exhibit tunable complex permittivity and conductivity through regulating MWCNT loading and thermal reduction temperature. The addition of MWCNT remarkably enhances the MA intensity of CGFs in low frequency. A minimum reflection loss value of −39.5 dB and average absorption intensity exceeding 22.5 dB in both C (4–8 GHz) and X (8–12 GHz) bands are obtained. For the optimized CGF, the qualified bandwidth with reflection loss less than - 10 dB reaches up to 16 GHz, which covers the whole measured range of 2–18 GHz and shares the widest qualified bandwidth among open literature reports. Furthermore, a specific MA performance of 12243 dB cm2 g−1 is realized, which is one of the best results among various MAMs. The synergistic effect of MWCNT and graphene and thus obtained three dimensional high loss multilevel network architecture are thought to be the primary causes for the excellent MA performance of CGFs.

A series of triblock copolymers, containing a CO2-switchable block poly(2-(dimethylamino)ethyl methacrylate) (PDM) block and two symmetrical hydrophilic blocks polyacrylamide (PAM), were synthesized using atom transfer radical polymerization (ATRP) method. The pH and conductivity tests showed that the triblock copolymer exhibited switchable responsiveness to CO2, i.e. a relatively low conductivity of solution could be switched on and off by bubbling and removing of CO2, and the triblock copolymer aqueous solution displayed a CO2-switchable viscosity variation. The changes were all attributed to protonation of tertiary amine groups in PDM blocks and proven by 1H-NMR. Cryogenic transmission electron microscopy and dynamic light scattering characterization demonstrated that the viscosity variation was the result of a unilamellar vesicle-network aggregate structure transition. The release of rhodamine B from the vesicles with and without CO2 stimuli showed the potential application in drug delivery domains; after CO2 bubbling, the drug release rate could be accelerated. Finally, reasonable mechanism of CO2-switchable morphology changes and CO2-induced drug release was proposed.

A carboxyl betaine amphoteric hydrophobic associative polyacrylamide (CBAHAPAM) was synthesized in water solution through radical polymerization, which was made of polyacrylamide, N,N′-dimethyl octadecyl allyl ammonium chloride (DOAC), 1-carboxy-N,N′-dimethyl-N-(3-methylacryl-amidopropyl) ethanaminium inner salt (CBMAA-1) and 2-acrylamide-2-methyl propanesulfonic acid (AMPS). Self-assembly associative properties in CBAHAPAM solution and the effects of salt and temperature on the associative behavior were investigated by the means of viscosimetry, rheological test, fluorescence spectroscopy, and environmental scanning electron microscope (ESEM). Results showed that the critical association concentration (CAC) of the CBAHAPAM was about 0.30–0.32 wt %. The addition of the calcium chloride made the apparent viscosity of CBAHAPAM solution improve drastically than NaCl. Meanwhile, CBAHAPAM solution with NaCl and CaCl2 showed up better heat and shearing resistance than CBAHAPAM solution itself. The network structures of CBAHAPAM aqueous or salt solution was observed by ESEM. NaCl and CaCl2 reinforced the network structures, which further indicated that CBAHAPAM solution had a excellent capacity of salt thickening.

In this study, nanosilica/crosslinked Polyacrylamide (PAM) microsphere with a core–shell structure is designed to make a functional material, where nanosilica provides the rigidity, stiffness and strength, the crosslinked PAM provides the flexibility and elasticity. The structure mentioned above make the resulting microspheres to be able to enter, expand, shut off and be removed from deep layers of oilfields. A methodology to create the nanosilica/crosslinked PAM microsphere with a core–shell structure has been developed, and molecular dynamic (MD) simulations are applied to successfully study the interaction between the microsphere and water in aqueous solution of nanosilica/crosslinked PAM microsphere and its swelling behavior. Results including the interaction energies (Einter) between nanosilica and crosslinked PAM, Einter between the microsphere and water molecules, radius of gyrations (Rg) of the microsphere, the radial distribution functions of microsphere-water pairs, the mean square displacements and the diffusion coefficients (D) of water are calculated and analyzed in detail. The experimental results of particle diameter tested from dynamic light scattering have been used to verify the simulation results of swelling behavior. The interaction between nanosilica/crosslinked PAM microsphere and water in aqueous solution and its swelling behavior are studied.

Here, we report a CO2 stimulus-responsive system with anionic surfactant sodium oleate (NaOA) and N, N, N′, N′, N″-Pentamethyldipropylenetriamine (PMDPTA). The microstructure transition from spherical micelles to worm-like micelles was confirmed by rheology measurements, dynamic light scattering (DLS), and cryogenic transmission electron microscopy (Cyro-TEM). There were three types of CO2−responsive groups in PMDPTA. However, because of PMDPTA ionization degrees, just one responsive group of PMDPTA could be ionized by CO2 to work with OA−, resulting in structure transformation from spherical micelles to worm-like micelles. Besides, this system could be switchable between low-viscosity fluid and high viscoelastic by CO2/N2.

The interaction between acrylamide acrylicacid copolymer (PAMAA) and the modified surface of nano-SiO2 is investigated using the molecular dynamic (MD) simulation. The binding energies (Ebinding) of interface, the concentration profiles of PAMAA and functional groups (carboxyl and acylamino) of corresponding model, the mean square displacements (MSD) and diffusion coefficients (D) of PAMAA in four systems with different modifiers are all calculated at 325 K in vacuum. Vinyl trimethoxy silane (VTEOS) shows best modification effect in the systems mentioned above. Furthermore, the effects of temperature on the interaction between VTEOS modified surface of nano-SiO2 and PAMAA are studied at 300, 325, 350, 375 and 400 K in aqueous solution. Interesting results show that, water molecular layer reduces with the increase of temperature, and then improves the interaction between PAMAA and VTEOS modified surface of nano-SiO2. The corresponding Ebinding of interface, the radial distribution functions (RDF) o...

A facile and effective route to prepare a pH and temperature dual-responsive surfactant micelle has been introduced based on hydrotrope potassium phthalic acid (PPA) and quaternary ammonium surfactants cetyltrimethylammonium bromide (CTAB). The system can be switched between viscoelastic solution and water-like fluid by adjusting pH values. In this paper, different binding abilities between the hydrotrope and surfactants have been demonstrated during the process of adjusting pH because the hydrotrope has different ionization degrees with the pH variation. And with the aid of rheological measurements and cryo-TEM observation, we discussed the different effects of the hydrotrope on surfactants at various pH values in detail and analyzed the possible aggregate transition mechanism of CTAB–PPA system induced by pH. Besides, this CTAB–PPA system has temperature-responsive property when pH

Polyacrylamide (PAM)-silica microspheres with core-shell structure are synthesized by inverse microemulsion polymerization in this study for the application of water shut-off due to high strength of nanosilica, crosslinked shell of PAM and strong interaction between PAM and silica. The core-shell microspheres flow into the high permeable layers along with injected water, meanwhile, swell after absorbing water and migrate into the deeper layer under the pressure by deformation, which efficiently increase the pressure of low and medium permeable layers, and decrease the loss of water into high permeable layers. Most resources of crude oil locate in low and medium permeable layers, and this work plays a very important role in the enhancement of recovery ratio of crude oil by new material. Transmission electron microscope (TEM), digital microscopes, dynamic light scattering (DLS), and thermogravimetric analysis (TGA) are used to study the shape, size and high temperature resistant of the microsphere. Moreover, capillary flow experiments, nuclear-pore film filtration, and sand packed tube displacement experiment are applied to analysis the mechanisms of deep profile control.

This research aims to clarify the role of magnesium oxide as a catalyst in the catalytic ozonation process. Nano-sized magnesium oxide was prepared by the sol–gel method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The catalytic performance of magnesium oxide was tested for the removal of phenol. The effect of initial pH, MgO nanocrystal amount, radical scavenger (t-butanol) and Rct was investigated to understand the catalytic ozonation mechanism of magnesium oxide with ozone. Experimental results illustrated that nano-sized magnesium oxide presented significant performance for the ozonation and catalyzed the removal of phenol from aqueous solution by ozonation with a radical pathway involving hydroxyl radicals, which was due to the activity of surface basic groups from magnesium oxide where the conversion of ozone to hydroxyl radicals occurred. Fourier transform infrared spectroscopy (FT-IR) and isoelectric point (IEP) analysis was applied to analyze the surface properties of the prepared nano-magnesium oxide. Activation energy (Ea) was calculated based on the Arrhenius principle equation. It reveals that phenol could enhance the density of surface hydroxyl groups and the introduction of magnesium oxide into the ozonation system does not alter the activation energy. Therefore, the prepared powder was found to be an efficient and promising catalyst for ozonation.

In this study, acrylamide (AM), allyl polyethylene-1000 (APEG), octadecyl dimethyl allyl ammonium chloride (DMDAAC-18), and sodium styrene sulfonate (SSS) were chosen to synthesize a quadripolymer (HPAAT) in which a hydrophobic association exists between the molecules. The critical concentration of the hydrophobic association was determined using fluorescence spectrophotometry. Furthermore, HPAAT formed films by adsorbing onto a carbonate rock surface. The molecular structure of HPAAT was characterized using Fourier-transform infrared spectroscopy and 1H-NMR spectroscopy, the results showed that the obtained product was consistent with the target product. The intrinsic viscosity was determined using an Ubbelohde viscometer. The molecular weight and dispersion exponent of HPAAT were determined using gel permeation chromatography. Addition of HPAAT into 20% HCl decreased the reaction rate of the acid rock obviously, even at a low viscosity. Variation of the reaction rate with time with different amounts of HPAAT was investigated using the volume of carbon dioxide gas produced. The adsorption and desorption of HPAAT on a carbonate rock surface were demonstrated using infrared spectroscopy analysis, scanning electron microscopy and ultraviolet spectrophotometry.

Branched polyethyleneimine (PEI) modified carbon nanoparticles (CNPs-PEI) with an average particle size of 20.1 nm were facile synthesized by hydrothermal treatment of citric acid and PEI. The PEI and oxygen-containing groups on CNPs-PEI endowed them with excellent dispersion stability in water. The tribological properties of CNPs-PEI as the water-based additives were evaluated under the four-ball mode, steel/steel contact and fixed load of 40 N by varying additive concentration. Amazingly, adding only 0.15 wt% of CNPs-PEI made the mean friction coefficient and wear volume of base liquid reduced by 53.4% and 94.9%, respectively, reflecting that the CNPs-PEI could be an effective additive of water lubrication. The wear scar surface analyses indicated that CNPs-PEI as additives promoted the formation of boundary lubrication films on the rubbing surfaces by mending and depositing effects, directly accounting for the distinguished friction-reducing, antiwear and oxidation resistance properties of CNPs-PEI.

A superwicking Ti-6Al-4V alloy material with a hierarchical capillary surface structure was fabricated using femtosecond laser. The basic capillary surface structure is an array of micropillars/microholes. For enhancing its capillary action, the surface of the micropillars/microholes is additionally structured by regular fine microgrooves using a technique of laser-induced periodic surface structures (LIPSS), providing an extremely strong capillary action in a temperature range between 23 °C and 80 °C. Due to strong capillary action, a water drop quickly spreads in the wicking surface structure and forms a thin film over a large surface area, resulting in fast evaporation. The maximum water flow velocity after the acceleration stage is found to be 225–250 mm/s. In contrast to other metallic materials with surface capillarity produced by laser processing, the wicking performance of which quickly degrades with time, the wicking functionality of the material created here is long-lasting. Strong and long-lasting wicking properties make the created material suitable for a large variety of practical applications based on liquid-vapor phase change. Potential significant energy savings in air-conditioning and cooling data centers due to application of the material created here can contribute to mitigation of global warming.

Surfactant extraction is the common method for treating oil sands. However, the recovery of traditional surfactant is difficult, and the oil emulsification phenomenon and generation of tailings are also caused easily. To develop the cleaner and sustainable approach for treating oil sands, a switchable water N, N, N′, N′-tetramethylhexanediamine (TMHDA) was used to improve extraction by surfactant sodium dodecyl benzene sulfonate (SDBS) solution with low concentration. Here, the TMHDA-containing SDBS solution has CO2 switchability because of the electrostatic interaction between SDBS solution and TMHDA with CO2 response, and can be also emulsify reversibly n-heptane, diesel oil, even crude oil, providing the possibility for separating oil from oil sands. The effective extraction of oil sands is performed by 1 mM (less than critical micelle concentration (CMC)) SDBS solution combined with TMHDA, which was also demonstrated by thermogravimetric analyzer, scanning electron microscope and elemental analysis. The residual oil content of oil sands is reduced to 0.515 wt% and 90.8% oil is removed by adding 0.15 g/mL TMHDA. Interestingly, oil is separated and fine sands is separated by introducing CO2, and the TMHDA-containing SDBS is recycled upon N2/65 °C.According to the detection of interfacial tension and Fourier Transform Infrared Spectroscopy (FTIR), it is demonstrated that the improved oil removal is ascribed to the adsorption of SDBS on solid surface and the reduced oil-water interface tension by the addition of TMHDA. Based on the evaluation of economic and environmental value, this sustainable approach exhibits potential application for treating oil sands in practical industry.

The self-thickening agent (TZXJ) consisting of acrylamide (AM), 1-carboxy-N, N′-dimethyl-N-(3-methyl-acrylamidopropyl) ethanaminium (CBMAA-1), [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (DMC) and N, N′-dimethyl octadecyl allyl ammonium chloride (DOAC) was synthesized and characterized. Effects of two kinds of surfactants 2-(bis(2-hydroxyethyl)(octadecyl)ammonio)acetate (ODB) and N,N,N-trimethyloctadecan-1-aminium bromide (STAB) on thickening performance, temperature resistance and shear resistance of TZXJ acid solution were studied via six-speed rotational viscometer and HAAK MARSⅢ Rheometer. Results showed that the ODB and STAB as accelerators can greatly enhance the thickening ability and temperature resistance of TZXJ self-thickening acid. After TZXJ self-thickening spent acid with accelerators was sheared at 140 °C for 60 min, the apparent viscosity of spent acid can reach 204 mPa s. It was found that the research results provided a new research idea that a small amount of long-chain cationic or amphoteric surfactants may greatly improve the application performance of hydrophobic associative polymeric self-thickening acid.

A viscosity reducer was prepared by using octadecyl methacrylate (SA) and styrene(S) as polymerization monomers and ethylene glycol dimethacrylate (EDMA) as branched monomers. When the dosage of viscosity reducer is 800 ppm, the viscosity reduction rate is more than 60%. By comparing the effect of different amount of viscosity reducer on the precipitation point, precipitation amount and asphalt particle diameter, it is found that the addition of viscosity reducer could increase the asphalt precipitation point and significouldtly decrease the precipitation’ amount and average particle size. In general, the addition of viscosity reducers could provide a good dispersion of asphaltene precipitation. The data from infrared spectroscopy, scouldning electron microscopy, XRD showed that the viscosity reducer could inhibit asphaltenes by changing the polarity of asphaltene molecules, causing hydrogen bonding, dispersing asphaltene molecules, adsorbing or embedding asphaltene molecular lamellae. And it has a good dispersion effect on asphaltene precipitation, which well inhibited asphaltene precipitation.

The oleylamine (OA)-modified carbon nanoparticles (CPs-OA) with particle sizes of 25–35 nm were synthesized by a facile one-pot pyrolysis method. As the OA molecules were covalently attached on the surfaces of CPs-OA, the CPs-OA exhibited good dispersibility in polyalphaolefin (PAO). Then the tribological behaviors of CPs-OA as the lubricating additives of PAO were investigated in detail. Under the four-ball mode and the load of 392 N, the CPs-OA showed the best friction-reducing and antiwear properties at the optimal concentration of 1.0 wt%. Specifically, in comparison with that of pure PAO, the mean friction coefficient and mean wear scar diameter of the 1.0 wt% CPs-OA/PAO suspension reduced by 47 and 30%, respectively. The friction-reducing and antiwear capabilities of CPs-OA strengthened with increasing load from 200 to 392 N and increasing test time from 240 to 480 min. In addition, the CPs-OA-based additives could work for a long time without weakening the lubrication capability. The synergistic effect of tribofilm, including PAO molecules and the CPs-OA layer, might account for the outstanding friction-reducing and antiwear capabilities of CPs-OA-based additives under boundary lubrication.

Macroscopic lossy foam has been expected to be the most promising candidate for lightweight high-performance microwave absorption (MA). However, inferior MA behaviors of conventional foams reported previously are disappointing. The emerging graphene foam (GF) has broken this paradoxical state of affairs. Here, series of GFs with various chemical compositions and physical structures have been prepared via a facile and controllable method and their MA performance is investigated in 2–18 GHz. The in-depth analyses of the GF’s composition, structure and MA property demonstrate that the MA performance of the GF is strongly correlated with the C/O ratio, conjugated carbon domain size and graphene framework’s microstructure. A maximum absorption value of −34.0 dB as well as 14.3 GHz qualified bandwidth with reflection loss below −10 dB is achieved for the GF with an ultralow bulk density of 1.6 mg/cm3, of which the average absorption intensity and the specific MA efficiency are much higher than those of the best available MA materials in previous literature. The composition & structure–performance relationship of MA foams is revealed. The balance between small interfacial impedance gap and high loss characteristic has wide implications in improving the MA performance of the GF and other porous materials.